Abstract:
The atmospheric trace gas, methane (CH4), affects the radiative heat balance of the earth. The sources of atmospheric methane are not well understood. Large air samples (1000-1400 litres) of methane are collected from a compressor system at Arrival Heights annually (since 1989) and samples are analysed for methane concentrations, the isotopic ratios of 14C/ 13C and 13C/12C and the characteristics ... and fluxes of sources and sinks are assessed. Sample collection is aimed at the clean sector of the sky from the West through North to East, throughout the year. Measurements of methane carbon isotopes and its concentration in the atmosphere in Antarctica will help to determine the geographic variation, transport and the type and distribution of the sources of methane from the northern hemisphere.

In-situ flask sampling: CO2, CH4, CO, N2O, 13CO2, 14CH4, 13CO, C180, 14CO. gas samples are collected from a mast 95 meters above ground level) in North sectors wind conditions only and above 5 knots. There are high pressure(~1000 litres, 800psi in 30L cylinder) and low pressure (~5 litres, 25psi in 2 litre flask) flask samples taken. Aire samples in the tanks and flasks are shipped back to NZ annually. Analysis is performed at NIWA's GAS LAB located at Greta Point Wellington. Gas chromatography (GC) and isotope ratio mass spectrometry (IRMS) employed in analysis. Data is held internally by NIWA and in the WDCGG database.

Quality
All of the data is held by NIWA Ltd., New Zealand and is available via the ftp site listed on this page. The data is also available via the Global Atmospheric Watch, World Data Centre for Greenhouse Gases (WDCGG). Please contact Dr Gordon Brailsford for more information.

Mak, J.E., Manning, M.R. and Lowe, D.C. 2000. Aircraft observations of δ13C of atmospheric methane over the Pacific in August 1991 and 1993: Evidence of an enrichment in 13CH4 in the Southern Hemisphere. Journal of Geophysical Research 105: 1329.